Natural solar light, i.e., sunlight, is a very desirable light source for interior use. Daylighting is the method of lighting a building's interior with full-spectrum, sunlight which supplements or replaces electric lighting during the daytime. There are many benefits to using daylight for illuminating areas within enclosed structures such as buildings. The use of daylight over artificial illumination for interior illumination provides a more balanced color rendering of objects which is more aesthetically pleasant and also reduces the need for energy to illuminate the interior of the building artificially. An additional benefit is the reduced amount of radiant energy produced by artificial illumination sources which can, in turn, reduce the amount of cooling needed to maintain a comfortable temperature within a building.
A problem that is frequently encountered when an area is illuminated using artificial light sources or natural daylight is how to spread the light adequately and evenly. Simple diffusers in the form of a sheet of translucent material can be used to spread light but, although they are inexpensive, they do not transmit light efficiently and are also unable to direct light in a controlled manner to where it is needed. Interior light shelves are often used on the inside of buildings to block sunlight into a building space and “bounce” the sunlight upward and deeper into the interior space. The light shelves are attached to the interiors of the buildings and extend outward away from the buildings facade. Artificial light shelves have been proven to reduce requirements for perimeter artificial lighting, thereby conserving electrical energy costs. In many cases, architects are designing curtain wall systems where light shelves are directly integrated into the structural members of the curtain wall.